Porous polymer membranes based on poly(vinylidene fluoride-trifluoroethylene)/poly(ethylene oxide) copolymers, P(VDF-TrFE)/PEO, are prepared through elimination (from partial to total) of PEO, leading to interconnected micropores in the polymer blends. Electrolyte uptake, thermal and mechanical properties depend on the amount of PEO present in the polymer blend. Further, the degree of crystallinity of PEO and the elastic modulus (E') of the polymer blend decrease with increasing PEO removal. Electrical properties of the polymer blend membranes are influenced by the porosity and are dominated by diffusion. The temperature dependence of the ionic conductivity follows the Arrhenius behavior. The ionic conductivity is the highest for the membranes with a volume fraction of pores of 44% (i.e., 90% PEO removal), reaching a value of 034 mS cm(-1) at room temperature. Battery performance was determined by assembling Li/C-LiFePO4 swagelok cells. The polymer blends with 90% PEO removal exhibit rate (124 mAhg(-1) at C/5 and 47 mAhg(-1) at 2C) and cycling capabilities suitable for lithium ion battery applications. ; FEDER funds through the "Programa Operacional Factores de Competitividade-COMPETE" ; FCT-Fundacao para a Ciencia e a Tecnologia PEST-C/FIS/UI607/2013 PEST-C/QUI/UI0686/2013 SFRH/BD/68499/2010 SFRH/BD/90313/2012 SFRH/BD/66930/2009 ; Matepro-Optimizing Materials and Processes NORTE-07-0124-FEDER-000037 ; "Programa Operacional Regional do Norte" (ON.2-O Novo Norte), under the "Quadro de Referencia Estrategico Nacional" (QREN), through the "Fundo Europeu de Desenvolvimento Regional" (FEDER) ; Ministerio de Economia y Competitividad, MINECO MAT2013-46467-C4-1-R ; FEDER ; VI National RDi Plan ; Iniciativa Ingenio ; Consolider Program ; CIBER Actions ; Instituto de Salud Carlos III ; Gören, A.; Costa, CM.; Tamaño Machiavello, MN.; Cintora-Juarez, D.; Nunes-Pereira, J.; Tirado, J.; Silva, MM. (2015). Effect of the degree of porosity on the performance of poly(vinylidene fluoride-trifluoroethylene)/poly(ethylene oxide) blend membranes for lithium-ion battery separators. Solid State Ionics. 280:1-9. doi:10.1016/j.ssi.2015.08.003. ; Senia ; 1 ; 9 ; 280